In general processes for manufacturing a semiconductor device, a nitride layer may be used as a hard mask, a spacer, an etch-stop layer, and the like. The silicon nitride layer may be formed on a pattern or a substrate by a chemical vapor deposition (CVD) process or an atomic layer deposition (ALD) process using a silicon source such as dichlorosilane (DCS) or hexachloro disilane (HCD; Si2Cl6) and a nitrogen source such as ammonia (NH3).
When a silicon nitride layer is formed by a low pressure chemical vapor deposition (LPCVD) process using dichlorosilane as a silicon source and using ammonia as a nitrogen source, the silicon nitride layer may have a dense structure. However, because a silicon wafer upon which the silicon nitride layer is formed may be exposed to a high temperature of above about 700° C. for a specified period of time, the silicon wafer may exhibit thermal damage in which impurities are diffused from the silicon wafer. As a result, a semiconductor device formed on the silicon wafer may have undesirable electrical characteristics, and conductive structures of the semiconductor device may show a greater extent of deterioration. To prevent this degree of thermal damage to the silicon wafer, a silicon nitride layer may be formed at a relatively low temperature.
When a silicon nitride layer is formed at a low temperature of below about 600° C. using hexachlorodisilane and ammonia, the silicon nitride layer may not possess a dense structure, and the silicon nitride layer may possess a high etching rate because, for instance, ammonia may not be easily dissociated at the low temperature. Since the silicon nitride layer may exhibit a high etching rate with respect to an etching solution for etching a nitride layer, the silicon nitride layer may not be employed as an etch stop layer or a hard mask layer in a semiconductor device. Additionally, because the silicon nitride layer may have undesirable electrical characteristics such as a low breakdown voltage, the semiconductor device including the silicon nitride layer may also have undesirable electrical characteristics. Thus, a source composition for forming a dense silicon nitride layer at a low temperature is desirable.
A conventional method for forming a nitride layer by a CVD process is described in Japanese Patent Laid Open Publication No. 1999-217673 and U.S. Pat. No. 6,106,898. In Japanese Patent Laid Open Publication No. 1999-217673, a nitrogen source including tertiary-butyl-hydrazine, having a dissociation rate higher than that of ammonia at a low temperature, is used for forming an innoxious nitride layer on a substrate.
In addition, Japanese Patent Laid Open Publication No. 2001-144325 describes a method for manufacturing a compound semiconductor device including a nitride-based material. According to Japanese Patent Laid Open Publication No. 2001-144325, hydrazine or substituted hydrazine is used for forming a nitride layer instead of ammonia, which as noted previously, may not be easily dissociated at a low temperature.
Although the above-mentioned methods use a nitrogen source for forming a nitride layer, a silicon source is not considered in the formation of a silicon nitride layer.